Enable client-gen for k8s.io/metrics

This commit turns on client-gen for k8s.io/metrics.  Clients are
generated for `k8s.io/metrics/pkg/apis/metrics` (both internal and
v1alpha1).  `k8s.io/metrics/pkg/apis/custom_metrics` uses a bespoke
client due to the unique nature of its paths.

hack/update-codegen.sh

@@ -104,3 +104,4 @@ ${informergen} \
 vendor/k8s.io/kube-aggregator/hack/update-codegen.sh
 vendor/k8s.io/sample-apiserver/hack/update-codegen.sh
 vendor/k8s.io/kube-apiextensions-server/hack/update-codegen.sh
+vendor/k8s.io/metrics/hack/update-codegen.sh

hack/verify-codegen.sh

@@ -27,6 +27,7 @@ kube::golang::setup_env
 vendor/k8s.io/kube-aggregator/hack/verify-codegen.sh
 vendor/k8s.io/sample-apiserver/hack/verify-codegen.sh
 vendor/k8s.io/kube-apiextensions-server/hack/verify-codegen.sh
+vendor/k8s.io/metrics/hack/verify-codegen.sh
 
 "${KUBE_ROOT}/hack/update-codegen.sh" --verify-only
 

staging/src/k8s.io/metrics/hack/update-codegen.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+
+# Copyright 2017 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+KUBE_ROOT=$(dirname "${BASH_SOURCE}")/../../../../..
+METRICS_ROOT=$(dirname "${BASH_SOURCE}")/..
+source "${KUBE_ROOT}/hack/lib/init.sh"
+
+# Register function to be called on EXIT to remove generated binary.
+function cleanup {
+  rm -f "${CLIENTGEN:-}"
+}
+trap cleanup EXIT
+
+echo "Building client-gen"
+CLIENTGEN="${PWD}/client-gen-binary"
+go build -o "${CLIENTGEN}" ./cmd/libs/go2idl/client-gen
+
+PREFIX=k8s.io/metrics/pkg/apis
+INPUT_BASE="--input-base ${PREFIX}"
+CLIENTSET_PATH="--clientset-path k8s.io/metrics/pkg/client/clientset_generated"
+
+${CLIENTGEN} --clientset-name="clientset" ${INPUT_BASE} --input metrics/v1alpha1 ${CLIENTSET_PATH} --output-base ${KUBE_ROOT}/vendor
+
+# we skip informers and listers for metrics, because we don't quite support the requisite operations yet
+# we skip generating the internal clientset as it's not really needed

staging/src/k8s.io/metrics/hack/verify-codegen.sh

@@ -0,0 +1,51 @@
+#!/bin/bash
+
+# Copyright 2017 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -o errexit
+set -o nounset
+set -o pipefail
+
+KUBE_ROOT=$(dirname "${BASH_SOURCE}")/../../../../..
+METRICS_ROOT=$(dirname "${BASH_SOURCE}")/..
+source "${KUBE_ROOT}/hack/lib/init.sh"
+
+DIFFROOT="${METRICS_ROOT}/pkg"
+TMP_DIFFROOT="${METRICS_ROOT}/_tmp/pkg"
+_tmp="${METRICS_ROOT}/_tmp"
+
+cleanup() {
+  rm -rf "${_tmp}"
+}
+trap "cleanup" EXIT SIGINT
+
+cleanup
+
+mkdir -p "${TMP_DIFFROOT}"
+cp -a "${DIFFROOT}"/* "${TMP_DIFFROOT}"
+
+"${METRICS_ROOT}/hack/update-codegen.sh"
+echo "diffing ${DIFFROOT} against freshly generated codegen"
+ret=0
+diff -Naupr "${DIFFROOT}" "${TMP_DIFFROOT}" || ret=$?
+cp -a "${TMP_DIFFROOT}"/* "${DIFFROOT}"
+if [[ $ret -eq 0 ]]
+then
+  echo "${DIFFROOT} up to date."
+else
+  echo "${DIFFROOT} is out of date. Please run hack/update-codegen.sh"
+  exit 1
+fi
+